Various anti-cancer agents are known which are currently in clinical use. Some of these, such as cyclophosphamide and chlorambucil, are derived from the highly toxic group of N-Lost derivatives which contain a so-called N-Lost group, that is, a bis(2-chloroethyl)amino group. The original N-Lost derivatives are known to have cancer-triggering properties and were formerly used as chemical weapons. However, clinically acceptable compounds, such as cyclophosphamide and chlorambucil, have been prepared by modifying the original N-Lost structure to produce analogues with a significantly reduced toxicity. Nevertheless, these analogues all contain chemically reactive chlorine which is believed to be essential for their biological activity. In contrast, N-methylformamide is known as an anti-cancer agent but contains no chemically reactive chlorine.